New guidelines on the management of pandemic H1N1 influenza were published recently by the Department of Health. They include guidelines on when to refer patients to hospital (see below) and an update on the epidemiology of the disease: fewer than 1% of cases are admitted to hospital; 12-15% of patients admitted to hospital go on to need high dependency or critical care; and mortality for hospitalised adults is around 6%. The presence of co-morbidities among those admitted appears to vary with age and is very low in young children:

Patients with underlying co-morbidities fare worse. Very few hospitalised young children (<20%) have co-morbidities, but this rises to 40% in 5-14 year-olds. Asthma is the commonest co-morbidity in children and young adults. Almost all (90%) hospitalised adults >65 years of age have at least one co-morbidity.

These co-morbidities are associated with poor outcomes according to the guidelines:

The risk of both hospital admission and death are strongly influenced by co-morbidities. In hospitalised adults significant risk factors for fatal outcomes include COPD, diabetes, and heart disease. Obesity appears to be a risk factor for requirement for critical care but not for death.

Predictive factors for ICU and death as outlined in the guidelines include: dyspnoea, requirement for supplemental oxygen, pneumonia on admission, and tachycardia in adults.

Referral criteria in primary care
Back in primary care, the guidelines suggest that referral criteria for hospital care should include any of the following: signs of respiratory distress, oxygen saturation of 94% or less in air, dehydration, shock, any signs of sepsis, altered conscious level and seizures.
The guidelines state that all patients assessed in primary care should have their peripheral oxygen saturation measured by pulse oximetry.

Measurement of peripheral oxygen saturation by pulse oximetry is essential to exclude hypoxaemia. Absence of cyanosis does not exclude hypoxaemia.

Does this mean that all GPs should be asked – or told – to ensure that they carry an oximeter? Should the recommendation be revised as it’s impractical or should all GPs who don’t carry an oximeter fork out for one? They only cost around £40 after all.

Overall, the widely expected second wave of swine flu appears to be approaching at a slower rate than anticipated. Some parts of the media are even speculating, perhaps over-optimistically, that the second peak may have already occurred. Last week in England there was a small rise (8%) in the estimated number of cases according to the Health Protection Agency. In Wales the number of GP consultations for flu-like symptoms went down, possibly as a result of the half-term school holidays.

Tom Nolan is a trainee GP in London.